He'd just left Hermione with a new pile of books in the library, and made his excuses and gone. He wasn't sure that Hermione had even noticed. Harry enjoyed just wandering the castle. In his first year, he'd found the Mirror of Erised, and that had made him always want to find more of the castles secrets.
A place as old as this, with it's history, and it's predecessors made him take a deep breath as if he could inhale their memory their deeds. He wanted to find what had made his father an animagus. Professor McGonagall always insisted that it was a rare skill, but the fact that James, Sirius and even Peter Pettigrew... were all animagi. Well, it just seemed as if there was more at play.
He tried to quiz Hagrid for clues, without giving away too much himself. He'd never come out and asked directly, although asking the Head of house didn't seem especially suspicious. So he liked to probe Minerva as much as he could. As the only animagus in the school (or at least the only registered one), he tried to be as flattering as possible.
He liked to suggest that Dumbledore was an animagus, and ask what his form was, what his patronus was...
He was lost in thought as he walked. It wasn't a corridor that was immediately familiar, but sometimes that was the way of it. Rounding a corner, he spotted Ron standing outside a door. There was something very odd, furtive about his behaviour, that stopped him from calling out to his friend.
He slipped back around the corner, and pulled out his cloak. It slid into place, and with a shimmer he was invisible. Harry was free to observe Ron's odd manner.
He was a look out... Glancing worriedly up and down at the least noise, even an unexpected breeze was enough to make Ron start to sweat and look unsettled.
A number of unpleasant ideas surface, a Slytherin curse or some kind of controlling geas. But as George and Fred burst out of the door, the reason became clearer.
There was a prank afoot.
George and Fred high fived each other, and smiled.
"They'll never discover it... until it's too late."
Ron's eyes darted between his brothers, clearly he wasn't in on the plan, as he listened intently for snippets of information, clues as to the prank.
"The Slytherin's will have a fun practice." George said before giving a ludicrously camp wink to his brother.